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The vending of prepaid electricity is finding widespread use in South Africa. STS (Standard Transfer Specification) specifies the way that tokens are used in the vending of prepaid electricity. This paper describes the development and implementation of an on-line vending system based on the Internet, aimed at enhancing the current off-line CVS (Common Vending System) specification that is used to generate the tokens. The proposed enhancements allow existing and readily available TCP/IP network infrastructure to be used as a transport mechanism for the sale of tokens. The physical security of the system is also improved, since it is no longer necessary to provide vendors with security modules at the point of sale. The proposed on-line system is compatible with the large number of installed EDs (Electricity Dispensers). This paper further describes the PKI (Public Key Infrastructure) required to implement the system, as well as the set of interactive exchanges required for the communication over the Internet.